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From: Jan Beulich <jbeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 3/2] x86/desc: Drop __HYPERVISOR_CS32
Date: Fri, 9 Aug 2019 14:50:16 +0200
Message-ID: <cf80bbdd-bddb-fb8f-f49b-1ef205422f67@suse.com> (raw)
In-Reply-To: <20190809123927.29751-1-andrew.cooper3@citrix.com>

On 09.08.2019 14:39, Andrew Cooper wrote:
> Xen, being 64bit only these days, has no use for a 32bit Ring 0 code segment.
> 
> Delete __HYPERVISOR_CS32 and remove it from the GDTs.  Also delete
> __HYPERVISOR_CS64 and use __HYPERVISOR_CS uniformly.

Long, long ago we've been considering doing this. Agreed,
nothing has surfaced to actually use it, but I wouldn't
subscribe to "has no use": We will need it if we ever want
to be able to run on 32-bit EFI _and_ invoke runtime
services there. Back then through the consideration against
dropping it was that we may want to invoke 32-bit BIOS
services (PCI, VGA) from the hypervisor.

Of course it wouldn't be terribly difficult to re-instate
these selectors / descriptors, but still. Nevertheless, if
you're convinced of the move despite the remarks above ...

> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Jan Beulich <jbeulich@suse.com>

Jan

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Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-09 10:34 [Xen-devel] [PATCH v2 0/2] x86/boot: cleanup Jan Beulich
2019-08-09 10:38 ` [Xen-devel] [PATCH v2 1/2] x86: define a few selector values Jan Beulich
2019-08-09 11:50   ` Andrew Cooper
2019-08-09 12:35     ` Jan Beulich
2019-08-23  2:38   ` Tian, Kevin
2019-08-09 10:40 ` [Xen-devel] [PATCH v2 2/2] x86/desc: Build boot_{, compat_}gdt[] in C Jan Beulich
2019-08-09 12:19   ` Andrew Cooper
2019-08-09 12:43     ` Jan Beulich
2019-08-09 13:07       ` Andrew Cooper
2019-08-09 13:18         ` Jan Beulich
2019-08-09 15:25           ` Andrew Cooper
2019-08-12  7:32   ` Jan Beulich
2019-08-12 10:36     ` Andrew Cooper
2019-08-09 10:41 ` [Xen-devel] [PATCH v2 0/2] x86/boot: cleanup Jan Beulich
2019-08-09 12:39 ` [Xen-devel] [PATCH 3/2] x86/desc: Drop __HYPERVISOR_CS32 Andrew Cooper
2019-08-09 12:50   ` Jan Beulich [this message]
2019-08-09 15:36     ` Andrew Cooper
2019-08-09 15:52       ` Jan Beulich

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